The problem is the size of the plates is often different. some are 3.5"x12" some are 5"x16" [rough sizes]. I use a 40 plate exchanger of the roughly 5"x16" size... I think it is good for 180K... It definitely works for my applications.

I sell from 10 plate all the way to 60 plate but don't know the btu off the top of my head. I will post the specs in the morning when I get back to the shop. Input temperature has a large effect and the exchangers are rated at two different temperatures.

I just got home from work and ran downstairs to check it out. I have a 30 plate exchanger. I'm just curious how much btu's get transfered from my OWB to inside the house. I guess it doesn't really matter seeing how I'm not going to use it once I hook up my EFM.

My experience with the exchangers is that they don't seem to give the performance that the catalog implys. We typically install a 50 plate for an average house and sub zero temps really seem to strain them. Of course this is heating the existing radiation which might work fine with 220 deg F off of the oil boiler but might be a little light at 180deg off of an out door boiler. Direct is always better if you can get away with it.

Steve.N wrote:My experience with the exchangers is that they don't seem to give the performance that the catalog implys. We typically install a 50 plate for an average house and sub zero temps really seem to strain them. Of course this is heating the existing radiation which might work fine with 220 deg F off of the oil boiler but might be a little light at 180deg off of an out door boiler. Direct is always better if you can get away with it.

Steve

In my professional engineering opinion once you start using heat exchangers in a hydronic heating system you have reached the limit of "rule of thumb" design. You need to do an "engineering" design not just use the nominal suggested typical, temperature drops, water flow rates, etc. I'm not surprised your experience with plate heat exchangers do not live up to data sheet expectations, particularly during high demand conditions.

The best text on "engineering" hydronic heating systems is "Modern Hydronic Heating for Residential and Light Commercial Buildings, 2E (Hardcover)" by John Siegenthaler, P.E. List price is over $150! I'm waiting for delivery of a discounted book from Amazon.com.

There are a couple of considerations for getting the most out of an exchanger... If your water flow is too slow,, then the heat from the supply water is absorbed by the heated water before the supply water makes it's way the full length of the exchanger,, the return water exiting the exchanger will be rather cool, only a few degrees above the heated water going to the baseboards..

If the rate of flow is increased in the heated water, the entire length of the exchanger will be at full temperature, and the heated water will be able to absorb more heat, this in effect increases the effective size [heated area] of the exchanger.

I have had two different pumps on my system, the lower flow and head pump [Taco 007] was not high volume enough with cold weather, the second pump, about double the capacity is up to the job.